Air Quality, Atmosphere & Health

, Volume 12, Issue 4, pp 471–489 | Cite as

An experimental and numerical study of air pollution near unpaved roads

  • José Ignacio Huertas CardozoEmail author
  • Daniel Fernando Prato Sánchez


Aiming to advance in the understanding of pollutant dispersion near roads, we measured, simultaneously, vehicle traffic, meteorological parameters, and 24-h average concentration of particulate matter (TSP, PM10, and PM2.5) at several locations downwind two unpaved roads, located on a flat region without any other relevant source of pollutants. We also implemented on a commercial software of computational fluids dynamics (CFD) an air quality model to simulate the dispersion of particles and gas-phase pollutants emitted from roads. Numerical results of monthly and daily averages of total suspended particles (TSP) concentrations showed high correlation with experimental measurements (R2 > 0.94). We found, numerically and experimentally, that the plots of pollutant concentrations vs distance to the road edge converge into a single curve when they are expressed in terms of dimensionless numbers. Profiles of vertical concentration sketch an exponential function at the road edge, an S shape downwind and a flat shape far from the road. Particle size distribution fits a Rosin-Rammler function with average diameter of ~ 7 μm. This distribution remains unaltered downwind the road, which implies that at any location within 1.5 km from the road, PM10 and PM2.5 concentrations are a constant fraction of TSP concentration. Experimental data confirmed this observation. Previous results can be used to determine the size of the area impacted by roads, identify mitigating and adaptive countermeasures, and to improve the accuracy of vehicular emission factors.


Computational fluid mechanics (CFD) Air quality modeling Environmental influence area Road emissions Unpaved roads 



Beta function parameters

a, b, k

Empirical constants


TSP concentration at surface level (μg/m3)

Ci, j

TSP concentration for i hour and distances j from the road edge (μg/m3)

\( \overline{C_j} \)

Annual TSP concentration at distance j from the road edge (μg/m3)


Dimensionless TSP concentration

d, \( \overline{d\ } \)

Particle diameter and average particle diameter (μm)


TSP mass emission rate per road area (g/s m2)


Emission factor for vehicle of size i in kg of TSP per vehicle and per km traveled (kg/VKT)


Dispersion factor

fPM10- fPM2.5

Fraction of PM10 and PM2.5 with respect to TSP

fk, q

The frequency at which wind speed of intensity k appears in the wind rose for direction q


Gravity (m/s2)


Von Karman universal constant


Fluid molecular viscosity (kg/m·s)

\( {\dot{m}}_{H,i} \)

Horizontal mass flow of pollutant i at a given distance to the road (kg/s)


Average weight of the vehicles of size j (Tons)


Spread parameter of the particle size distribution function


Number of vehicle of size i

Rc, i

Mass emission ratio

ρ, ρp

Fluid and particle density (kg/m3)


Silt content of road surface material


Schmidt number


Wind speed at height z (m/s)


Friction velocity (m/s)


Mean wind speed in the x direction (m/s)


Dimensionless speed ratio


Settling speed (m/s)


Road width (m)


Particle emission speed (m/s)


Distance from the road edge (m)


Equivalent distance from the road (m)


Non-dimensional distance to the road edge


Rosin-Rammler particle size distribution


Height (m)


Surface roughness (m)


Non-dimensional wall distance



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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.School of Engineering and ScienceTecnológico de MonterreyMonterreyMexico

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